Let me start off by saying I'm not an expert in these matters, but I can give you my personal opinion.
I really don't think the placement of a label on the disc should be causing any problems. I know you'll find sources out there that are adamant you don't use labels but if you're using a good quality label with adhesive that's not going to cause damage to the disc I really don't see the problem unless you lifted the label up to reposition it after the adhesive came in contact with the disc. That could cause a problem.
My understanding of the dvd repair machines is that they simply buff out the discs to make them readable again. If this is by some chance a label related problem then a repair machine is going to be of no use to you. Ditto it it's bad burns or bad discs.
Cheap discs? That's very possible. What brand did you buy? Have you used the specific brand of disc you're having this problem with in the past with no issues? If you bought Dynex then I'd be willing to say that very well could be the problem. I personally spring the little bit of extra cash to buy Verbatims and I've never had any issues to speak of with them. I don't want to jump full fledged on the Memorex bandwagon because they went through a phase of being some of the crappiest discs on the market, but I've tried them again since I've seen they're now owned by Imation (which is a brand I trust) and I've seen that many of the issues I had with them before seem to have been corrected now that Imation owns Memorex.
There are other possible causes as well. What software are you using to burn your files? Is your burner dying on you? Is your dvd player dying on you? I once had a player that began it's death throes by freezing and skipping badly on burned DVDs.
Again, these are all just opinions based on my personal experience with burned discs. Hopefully I've at least given you a lead on solving your problem if nothing else.
